1. Field of the Invention
This invention relates to floor structures of buildings and more particularly to floor structures incorporating a barrier to the passage of water vapor and gases.
2. Brief Description of the Prior Art
In climates which do not experience winter temperatures low enough to cause substantial freezing of the ground, houses and light commercial buildings are often constructed on relatively shallow foundations, with the ground floor, typically a concrete slab, supported directly on grade. A finish floor, e.g., asphalt tile, wood, or the like, can be installed over the concrete slab by simply setting it in a mastic adhesive trowelled onto the substrate. In geographical areas where the water table is relatively close to the surface, however, this construction presents certain problems when wood flooring is laid directly on the concrete support, because water vapor migrating from the moist soil through the concrete slab can cause the wood flooring to swell and warp. More recently, radon infiltration from the soil into buildings has been recognized as a health hazard in certain regions, and attempts have been made to devise floor structures to exclude radon.
In order to prevent water vapor damage, it is customary to install a vapor barrier between the upper surface of the concrete slab and the wooden flooring. One known type of floor structure having a vapor barrier is a multi-layer structure constructed by applying a cutback asphalt adhesive over the concrete slab, laying down a synthetic resin vapor barrier, e.g., a 6-mil polyethylene film, on the asphalt adhesive, trowelling a cutback adhesive over the barrier layer, and setting the wood floor in the adhesive. While this construction is effective, the flammable and odoriferous character of the cutback asphalt as well as its toxicity and suspected carcinogenicity have caused this method of installing a vapor barrier to fall into disfavor. Alternative adhesives have been tried, such as epoxy-based adhesives, but these have not been entirely satisfactory. Epoxy adhesives are formulated from ingredients that must be mixed in exact proportions and must be mixed very thoroughly, with the consequence that they are difficult to use. Low viscosity sodium silicate adhesives have also proved unsatisfactory. An effective structure is achieved by installing a low cost vinyl roll flooring over the concrete slab and laying the wood floor on top of it, but this construction amounts to laying two floors.
Certain structures incorporating multiple layers have been described in a number of U.S. Patents. U.S. Pat. No. 3,712,845, to Hartung, discloses a substrate surface covered with a continuous sheet of synthetic resin upon which are laid textile tiles having a synthetic resin backing. The synthetic resin backing is applied to the fabric as a hot melt. The tiles are simply laid on the synthetic resin sheet, with the backing and sheet materials being elected to have sufficient adhesion to prevent warping, shifting, or the like, of the carpet tiles. Neither assembly of the structural elements with curable adhesive nor vapor barrier properties of the structure are disclosed in the Hartung patent.
A roofing construction using a metal foil vapor barrier is disclosed in U.S. Pat. No. 2,708,170, to Hampton. A base sheet, comprised of one or more layers of asphalt saturated felt is applied to a roof, covered with a metal foil vapor barrier, e.g., aluminum foil, and the laminate is then covered with a roofing seal or cement in which rock chips are embedded.
A wall structure incorporating conventional gypsum wallboard having a paper-metal foil laminate adhered to its exterior-facing surface to serve as a vapor barrier is disclosed in U.S. Pat. No. 4,077,168, to Smith. The foil side of the paper-foil laminate is adhered to the wallboard, leaving the paper side exposed to provide a surface that can be securely fastened to the building structure, e.g., studs or joists, with an adhesive.
In view of the deficiencies in the known methods of installing a floor having a vapor and gas barrier, a need has continued to exist for a floor structure that resists penetration of vapor or gas and is constructed of materials that are environmentally and industrially acceptable.